New Yorkers are spending more than the price of the average American home — on storage units.

Tribeca’s 56 Leonard just sold a 200-square-foot unit for $300,000. That’s $1,500 a square foot for a metal cage in the basement of the future luxury skyscraper.

“It’s unbelievable,” said Elizabeth Unger of Corcoran Sunshine, which is marketing the 60-story building.

“But when you compare New York to the rest of the country, we’re limited with space. We don’t have the garage or basement, and closet space is at a premium.”

The 145-unit, modernist glass tower resembling a stack of Jenga blocks is slated to open in the summer of 2015.

Buyers are paying $2,000 to $6,000 a square foot for homes in the high-rise, where a four-bedroom penthouse is in contract for $47 million.

For the subterranean storage, people are shelling out as much as $1,800 a square foot.

The building’s 76 basement cages start at $72,000 for 40 square feet and $214,200 for 119 square feet and can be combined to create larger underground closets.

They have no walls, carpeting or shelves but are made of tightly woven crates secured with padlocks. For a monthly maintenance fee of up to $20, they include electricity and security cameras.

“Storage is not an afterthought,” Unger told The Post. “People come in and ask about it. ‘Do you have a gym, do you have a doorman and do you have storage?’

“Is it the wave of the future? Absolutely,” she added.

Designed by architects Herzog & de Meuron, the modernist building is 80 percent spoken for with $900 million in sales.

The $300,000 storage cage went to the millionaire buyers of a three-bedroom pad on an upper floor. The developer wouldn’t say which apartment, but the three-bedrooms run from $5 million to $9.25 million.

Meanwhile, the average sale price for existing homes nationwide was $260,600 in July, according to the National Association of Realtors.

For the price of the Tribeca storage closets, buyers could get a mountain home in Granby, Colo., where a five-bedroom, three-bath pad is on the market for $291,900. In Springfield, Ohio, an elegant three-story home with five bedrooms and four baths is available for $300,000.

But in a city where even a parking spot goes for $1 million, it’s no surprise that the storage vaults run steep.